Turbine engine fan housing abradable material removal tool and method of abradable material removal

ABSTRACT

Devices and methods by which an amount of an abradable material may be removed from the housing of a gas turbine engine. A device of the invention is generally comprised of an abradable material removal tool having a curved abradable material contacting base with a handle or other gripping portion extending therefrom. An abrasive material, such as a sheet of sand paper, may be associated with a contacting surface of the base. The base is dimensioned and provided with a shape that permits its insertion between adjacent leading and trailing fan blades of an engine fan. A manual back-and-forth rotation of the fan while the abradable material removal tool is positioned between the fan blades and depressed against the surface of the abradable material will result in a controlled removal of abradable material along a path traced by the tips of the fan blades.

BACKGROUND

A number of gas turbine engines are known and would be familiar to one of skill in the art. Three common types of jet aircraft gas turbine engines are the turboprop, the turbojet and the turbofan, although more exotic and application-specific embodiments also exist. Each engine achieves the desired end result of generating thrust that may be used to propel an aircraft, albeit in a somewhat different manner.

All gas turbine engines generally include a forward intake section for capturing and feeding air to the engine. The intake section is typically followed by a compression section where the incoming air is compressed by a rotating compressor and accelerated. The compressed air is then passed into a combustion section, where heat is added through the burning of fuel to produce a high-velocity gas stream that is passed to a turbine section. In the turbine section, the high-velocity gas stream rotates a turbine, which is connected to and rotates at least the compressor.

In a turboprop engine, the turbine portion of the gas turbine engine is connected by a shaft to the compressor and to a propeller that (typically) resides forward of and outside of the turbine engine housing. Rotation of the turbine thus causes a corresponding rotation of the propeller, which displaces the surrounding air and produces thrust. In a turbojet engine, the turbine is still connected to the compressor, but all of the thrust is typically generated by passing the high-velocity gas stream through a propelling nozzle at it exits the engine. The nozzle constricts the flow of the exiting gas stream, thereby maximizing the velocity thereof.

Of particular interest in the present application is the turbofan engine. Like the turboprop and turbojet engine, a turbofan engine also includes a forward air intake, followed by a compressor section, a combustion section, a turbine section and an exhaust section. In a turbofan engine, however, a rotating fan of typically large diameter resides upstream of the compressor section and within the engine housing, which may also be referred to as a nacelle, case, or duct (hence the “ducted fan” nomenclature often associated with turbofan engines). The fan is driven by the turbine along with the compressor. The fan is used to increase the amount of air that is passed through the engine, thereby increasing the thrust produced by the engine.

Turbofan engines normally come in two variations—low bypass engines and high bypass engines. These designations refer to the ratio of the amount of air that passes through the combustion portion of the engine to the amount of air that passes around the combustion section (i.e., through only the fan). In either case, the fan is typically designed to move as much air as possible through the engine, so the tips of the fan blades normally rotate in very close proximity to the inside of the fan housing. The resultant minimized gap between the fan blades and the interior of the fan housing can be problematic, as gravity, dynamic forces of rotation or flight movement, and/or different rates of thermal expansion, may result in contact between the tips of the rotating fan blades and the interior of the fan housing. This contact typically occurs, but is not restricted to, approximately the 5:00 and 7:00 positions within the fan housing (i.e., along a bottom portion of fan rotation). At a minimum, such contact may damage or cause a wearing of the fan blade tips. If blade-tip-to-housing contact is sufficiently severe, however, engine damage or engine failure may result.

Turbofan engine designers are aware of and usually anticipate the possibility of contact between the fan blade tips and the interior of the engine housing. To this end, the housing interior surrounding the fan is commonly covered with an abradable material, such as in the form of a circumferential contact strip. The abradable material is sacrificial in nature, meaning that it is designed to wear away upon contact with the tips of the fan blades. A number of useable abradable materials would be familiar to one of skill in the art.

When contact between the fan blade tips and the abradable material of the fan housing is detected, it may be desirable to slightly increase the blade tip-to-abradable material minimized gap in the area of contact. The amount of material removed is normally very small—on the order of thousandths of an inch, for example. This makes it very difficult, if not impossible, to acceptably effectuate the removal of abradable material with a power tool. It is also desirable that the abradable material be removed in a manner that follows the contour/curvature of the fan housing and associated abradable material layer. Consequently, it is also very difficult, if not impossible, to consistently effectuate the removal of abradable material by hand—such as by means of a hand-held sandpaper sheet or the like.

It can be understood from the foregoing comments that there is a need for a device and method of efficiently, accurately and consistently removing small amounts of abradable material from the interior of a gas turbine engine housing. Devices and methods of the invention satisfy this need.

SUMMARY

The invention is directed to devices and methods by which small amounts of gas turbine engine housing abradable material may be removed along the path of a rotatable engine fan. A device of the invention is generally comprised of an abradable material removal tool having an abradable material contacting base with a handle or other gripping portion extending therefrom. The base is preferably formed from a substantially rigid material with a curved profile that matches the curvature (i.e., circumference) of the abradable material contact surface. A rigid or semi-rigid rib may extend from a top surface or other portion of the base. The rib preferably extends substantially perpendicularly upward therefrom to facilitate handling and use of the tool (i.e., to act as a handle), and may also help to maintain the desired curvature of the base.

An abrasive material, such as a sheet of sand paper, may be affixed to the contacting surface 85 of the base—with the abrasive material facing outward therefrom. The fixed curvature of the base allows the curvature of the abradable material to be substantially maintained when the tool is used in an abradable material removal operation.

The base 55 is also dimensioned and provided with a shape that permits its insertion between adjacent leading and trailing fan blades 20 of the turbofan engine 5. Consequently, a hand-generated back-and-forth rotation of the fan 15 while the abradable material removal tool is positioned therebetween and depressed against the surface of the abradable material, will result in a controlled removal of abradable material along a path traced by the tips of the fan blades.

BRIEF DESCRIPTION OF THE DRAWINGS

In addition to the features mentioned above, other aspects of the present invention will be readily apparent from the following descriptions of the drawings and exemplary embodiments, wherein like reference numerals across the several views refer to identical or equivalent features, and wherein:

FIG. 1 depicts a portion of an exemplary turbofan jet engine, wherein the blades of a fan portion thereof are shown to be rotatably mounted within a fan housing having an abradable material lining;

FIG. 2 is a perspective view of one exemplary embodiment of an abradable material removal tool of the invention;

FIGS. 3A-3C are front, side and top views, respectively, of the exemplary abradable material removal tool of FIG. 2;

FIG. 4 shows the exemplary abradable material removal tool of FIG. 2 with a trimmed sheet of sand paper removably affixed to an abradable material contacting surface of a base portion thereof; and

FIG. 5 shows the exemplary abradable material removal tool of FIG. 2 properly positioned for use within a housing and between the fan blades of an exemplary turbofan jet engine fan.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENT(S)

An intake portion of one exemplary embodiment of a turbofan jet engine 5 is depicted in FIG. 1. As shown, the engine 5 includes a housing 10 within which rotates a fan 15. As described previously, the fan 15 is rotated by a turbine-driven shaft (not visible) to push air through the engine 5. The fan 15, can be seen to have a plurality of circumferentially spaced fan blades 20 that are designed and oriented to produce an airstream that will travel rearward through the engine when the fan is rotated. Each of the fan blades 20 terminates in a flared blade tip 25 at its free end.

An abradable material lining 30 is visible along the inside of the fan housing 10, along the rotational travel path of the blade tips 25. During fan rotation, a minimized gap 35 separates the blade tips 25 from an adjacent (contact) surface 40 of the abradable material lining 30. In this particular example, an area of contact 45 between the blade tips 25 and the abradable material lining 30 is visible. It may be desirable to remove an amount of the abradable material lining 30 in this area 45 so as to minimize or eliminate further contact thereof by the blade tips 25 of the fan 15.

One exemplary embodiment of an abradable material removal tool 50 according to the invention is depicted in FIGS. 2-4. For purposes of illustration, the abradable material removal tool 50 is described below with reference to its use on the turbofan jet engine 5 of FIG. 1. However, the abradable material removal tool may also be used with other jet engines.

As shown, the abradable material removal tool 50 includes an abradable material contacting base 55 having a leading end 55 a, a trailing end 55 b, and a curved profile C that corresponds to the curvature (i.e., circumference) of the abradable material contact surface 40 when the abradable material removal tool is in a proper working orientation (see FIG. 5). The base 55 is preferably formed from a rigid or substantially rigid material that will retain the desired curvature.

For reasons described in more detail below, the abradable material contacting base 55 is also of a size and shape that allows it to fit accurately between adjacent blades 20 of the jet engine fan 15 and to trace the path followed by the blade tips 25. More particularly, the abradable material contacting base 55 preferably includes a long edge 60, and a shorter opposite edge 65 having a leading bevel or taper 70.

A rigid or semi-rigid rib 75 may extend from a top surface 80 or other portion of the base 55. The rib 75 preferably, but not necessarily, extends substantially perpendicularly upward therefrom to facilitate handling and use of the tool 5 (i.e., to act as a handle). The rib 75 may also help to maintain the desired curvature C of the base 55 or, in embodiments where the base itself is not sufficiently rigid to do so, may actually establish and maintain the curvature of the base.

The rib (handle) 75 may be of virtually any height and shape. However, the bottom edge thereof is preferably shaped to conform to the curvature C of the base 55. The rib 75 may be secured to the base 55 by any technique known in the art, such techniques being at least somewhat dependent on the materials used to construct the base and rib. When the base 55 and rib 75 are comprised of plastic materials, attachment of the rib to the base may be accomplished by, for example, adhesive bonding, vibratory welding, etc. Alternatively, the base 55 and rib 75 may be a unitary structure formed by molding, casting, etc. The rib 75 may also include cutouts/holes and/or protrusions of various shape and size for purposes of improving the handling and use of the abradable material removal tool 5.

Use of the abradable material removal tool 5 to remove an amount of abradable material from within a turbofan housing also requires an abrasive material. To that end, this particular exemplary abradable material removal tool 5 is shown in FIG. 4 with a sheet of sandpaper 90 removably affixed to the abradable material contacting (bottom) surface 85 of the base 55. The abrasive material side of the sandpaper sheet faces away from the base 55, such that the abrasive material is exposed and will be in contact with the abradable material lining 30 of the engine housing 10 when the abradable material removal tool 5 is properly used. When an abrasive material sheet or other abrasive material carrier is affixed to the abradable material contacting surface 85 of the base 55, it is preferably trimmed or otherwise provided with substantially the same planform shape as the base. This helps to ensure that abradable material removal will occur only under the footprint cast by the base 55 of the abradable material removal tool 5.

An abradable material removal tool of the invention is not limited to use with an abrasive material sheet, such as the sheet of sandpaper 95 shown in FIG. 4. For example, the base of an abradable material removal tool of the invention may instead be provided with an abradable material contacting surface that is inherently abrasive, such as through molding, casting, etc. The base of an abradable material removal tool of the invention may also instead have an abrasive material (without or without a carrier element) permanently adhered to the abradable material contacting surface of its base, or may have a base with an abradable material contacting surface into which an abrasive material has been embedded. The base of an abradable material removal tool of the invention may also be partially or fully impregnated with an abrasive material so that use of the tool may continue as the base wears.

As mentioned above, the base 55 of the abradable material removal tool 5 is dimensioned so as to fit between adjacent leading and trailing fan blades 20 of the fan 15. It is preferred that the base 55 be dimensioned such that the abradable material removal tool 5 may be easily inserted between adjacent fan blades 20, while also being properly oriented by the blades. The abradable material removal tool 5 is shown in such an orientation in FIG. 5, with the abrasive material side of the sandpaper sheet 90 residing against the surface 40 of the abradable material lining 30.

Referring still to FIG. 5, it can be observed that the planform shape of the base 55 of the abradable material removal tool 5 preferably results in the base tracing the path of the fan blade tips 25 when the fan 15 is rotated while the tool resides between fan blades 20 thereof. More specifically, the tapered portion 70 along the leading end 55 a of the base 55 is designed to substantially follow an imaginary line between leading tips 25 of adjacent fan blades 20 when the abradable material removal tool 5 is properly located between said fan blades.

With the abradable material removal tool 5 positioned substantially as shown in FIG. 5, an amount of the abradable material 30 may be slowly and deliberately removed by manually rotating the fan 15 back-and-forth through a desired arc while the abradable material removal tool is pressed toward the engine housing to maintain contact between the abrasive material (e.g., sandpaper sheet 90) and the surface 40 of the abradable material. The abradable material removal tool 5 may be depressed against the surface 40 of the abradable material lining 30 during fan rotation by, for example, a finger(s) of the user of the tool. Alternatively, it may be possible to produce an abradable material removal tool 5 where the rib 75 thereof may be clamped to one of the fan blades 20 in a manner that maintains a desired amount of pressure between the base 55 of the tool and the surface 40 of the abradable material 30. In any case, use of the abradable material tool 5 as described will result in a controlled removal of abradable material 30 along a path traced by the tips 25 of the fan blades 20.

While certain embodiments of the present invention are described in detail above, the scope of the invention is not to be considered limited by such disclosure, and modifications are possible without departing from the spirit of the invention as evidenced by the following claims: 

What is claimed is:
 1. A gas turbine engine abradable material removal tool, comprising: a base having a curved profile that substantially mimics the curvature of an abradable material lining of a gas turbine engine of interest, the base having a leading end with a tapered edge, a trailing end, and an abradable material contacting surface adapted for association with an abrasive material; and a rib extending upward from the base.
 2. The abradable material removal tool of claim 1, wherein the base is comprised of a rigid material that retains the curved profile without assistance.
 3. The abradable material removal tool of claim 1, wherein the base is comprised of a semi-rigid material and the curved profile thereof is retained with assistance from the rib.
 4. The abradable material removal tool of claim 1, wherein the rib is attached to the base.
 5. The abradable material removal tool of claim 1, wherein the rib and the base are a unitary molded structure.
 6. The abradable material removal tool of claim 1, wherein the rib includes at least one cutout for facilitating use of the rib as a handle.
 7. The abradable material removal tool of claim 1, further comprising an abrasive material affixed to one side of a carrier sheet, an opposite side of the carrier sheet removably affixed to the abradable material contacting surface of the base.
 8. The abradable material removal tool of claim 7, wherein the abrasive material and carrier sheet are parts of a sheet of sandpaper.
 9. The abradable material removal tool of claim 8, wherein the shape of the sheet of sandpaper is substantially duplicative of the planform shape of the base.
 10. The abradable material removal tool of claim 1, further comprising a texture on the contacting surface of the base that serves as the abrasive material.
 11. The abradable material removal tool of claim 1, further comprising an abrasive material embedded in the contacting surface of the base.
 12. The abradable material removal tool of claim 1, wherein the base is dimensioned to fit between adjacent blades of a fan of a gas turbine engine of interest.
 13. The abradable material removal tool of claim 12, wherein the taper along the leading end of the base will substantially lie on an imaginary line between leading tips of the fan blades when the tool is properly located between adjacent fan blades of the fan.
 14. A tool for removing an amount of an abradable material lining located within an engine housing and surrounding a fan of a turbofan jet engine, comprising: a rigid base having a curved profile that substantially mimics the curvature of the abradable material lining, the base having a leading end with a tapered edge, a trailing end, and an abradable material contacting surface adapted for association with an abrasive medium; a rib extending upward from the base to act as a handle for gripping and manipulating the tool; and an abrasive material associated with and exposed along the abradable material contacting surface of the base; wherein the base is dimensioned to fit between adjacent blades of a fan of a gas turbine engine of interest and shaped such that the taper along the leading end of the base will substantially lie on an imaginary line between leading tips of adjacent fan blades when the tool is properly located between adjacent fan blades of the fan.
 15. The abradable material removal tool of claim 14, wherein the rib is attached to the base and the curvature of the rib along the line of attachment is substantially the same as the curvature of the base.
 16. The abradable material removal tool of claim 1, wherein the abrasive material is a sheet of sandpaper that is removably affixed to the abradable material contacting surface of the base, the sheet of sandpaper having substantially the same planform shape as the base.
 17. A method of selectively removing an amount of an abradable material lining located within an engine housing and surrounding a fan of a turbofan jet engine, comprising: providing an abradable material removal tool, the abradable material removal tool further comprising: a base having a curved profile that substantially mimics the curvature of the abradable material lining of the turbofan engine of interest, the base having a leading end with a tapered edge, a trailing end, and an abradable material contacting surface substantially covered with an exposed abrasive material, and a rib extending upward from the base, the rib acting as a handle for gripping and manipulating the tool; locating the tool between adjacent blades of the turbofan engine fan such that the abrasive material is in contact with the abradable material lining; orienting the tool such that the taper along the leading end of the base will substantially lie on an imaginary line between leading tips of the adjacent fan blades; if the selected adjacent fan blades between which the tool is located are not already located in an area of desired abradable material removal, manually rotating the fan to so that the blades and tool are so located; pressing the tool against the abradable material lining with some amount of force; and manually rotating the fan back-and-forth through an arc sufficient to pass the tool over a desired area of abradable material removal while maintaining pressure on the tool.
 18. The method of claim 17, wherein the exposed abrasive material of the abradable material removal tool is a sheet of sandpaper that is removably affixed to the abradable material contacting surface of the base.
 19. The method of claim 17, wherein the base of the abradable material removal tool is comprised of a rigid material that retains the curved profile without assistance.
 20. The method of claim 17, wherein the abradable material removal tool is pressed against the abradable material lining of the engine during fan rotation by the finger(s) of a user. 